Across a variety of outdoor images, I had been puzzled over strange localized deformations from aperture to aperture even on rigid subjects, cases where there had been wind (so the camera could be jiggled a bit), but also very high shutter speeds in use. Part of the weirdness across apertures could be due to the poor focusing precision of the GFX and perhaps a bit of focus shift, but lacking the expected uniformity associated with those effects, my conclusion (to my chagrin) is that the deformations are in fact related to the rolling shutter effect caused by an all-electronic shutter.